Portable USB hubs and the Surface (Pro)

Before I start I guess I'll give my story. I plan on replacing my 11 inch MacBook Air running Windows 7 with the Surface Pro when its released. That thing looks awesome but I have one big concern. The Surface only has one USB port! I don't think I can live with one USB port, so I'm trying to learn more about what my USB hub options are. I mainly use my computer's USB ports to transfer files from one external hard drive to another. Does anyone know any portable USB hub options that will allow me to do this? I know there are USB hubs I can buy that require a power supply, but that kills the whole idea of what I think the Surface should be. Does what I'm asking for even exist? Does anyone know if they make battery powered USB hubs if it comes down to that?